This invention relates to printers, and more particularly to encoding systems for media advance systems.
Printers, such as ink-jet printers, can typically employ a media drive system to advance the print media along a media path through a print zone. The print zone in a typical ink-jet printer is located beneath the nozzles of the ink-jet print cartridges. For swath-type printers, the print cartridges are typically mounted on a carriage which moves along a carriage scan axis transverse to the media path, and ink droplets are ejected in a controlled fashion as the carriage is driven.
Accurate control of the carriage drive and the media advance is needed to achieve good print quality. If the media and the print elements cannot be accurately positioned while the ink droplets are ejected onto the media, the image quality will degrade. To achieve accurate control of the carriage drive, an encoder system is typically used to monitor carriage motion and position in response to commanded motor-driven movements.
This invention addresses problems associated with the accurate media positioning with a belt drive.
In accordance with an aspect of the invention, an encoding system is described for a media handling system including an endless belt. The encoding system includes encoding indicia associated with the endless belt. A first encoder transducer is responsive to the encoding indicia to provide a first encoder signal. A second encoder transducer is responsive to the encoding indicia to provide a second encoder signal, the second encoder transducer spatially separated from the first encoder transducer. An encoder processor is responsive to the first encoder signal and the second encoder signal to determine position data regarding the endless belt.
According to another aspect of the invention, the processor is adapted to compensate for variations in the encoder indicia pitch caused by belt temperature differentials.
According to a further aspect of the invention, a method is described for providing belt position information for a media handling system including an endless belt having encoder indicia associated with the belt. The method includes:
reading a first encoder signal from a first encoder transducer responsive to the encoding indicia;
reading a second encoder signal from a second encoder transducer responsive to the encoding indicia, the second encoder transducer spatially separated from the first encoder transducer;
processing the first encoder signal and the second encoder signal to determine position data regarding the endless belt.